1. Technical Field
The present invention relates to a process and an arrangement for producing airborne fibers from continuous lengths of thread bundles of fiber material.
2. Description of Related Art
In the manufacture of absorbent articles such as diapers, incontinence pads, sanitary towels and the like, a number of different types of material are used made up of various types of synthetic fibers. The materials most commonly encountered are various types of so-called non-woven materials, which are mainly used as liquid-permeable surface layers of absorbent articles. The liquid-permeable surface layers are arranged on that side of the article which in use is turned towards the user. Another common type of material made up of synthetic fibers are so-called waddings, which is a material placed directly inside the liquid-permeable surface layer of the absorbent article and functioning as a first temporary storage material for the liquid getting into the article.
There are also other applications of synthetic fiber material in absorbent articles.
The basic material for the manufacture of synthetic fiber material for absorbent articles are continuous lengths of thread bundles (tow rope), which are cut to predefined lengths in a separate process before the non-woven material or the wadding can be manufactured. WO-A1-93/11288 shows an arrangement for feeding thread bundles of synthetic fiber material to a cutting arrangement in which the thread bundles are cut to specific lengths.
The cut fibers are then normally baled for delivery to a manufacturer of non-woven material or wadding material.
Regardless of whether they go for non-woven manufacture or wadding manufacture, the fibers in the fiber bales are separated from one another in a first stage, following which the fibers are fed into a manufacturing process in which a so-called fiber layer is created. A common technique for creating a fiber layer is carding. The fiber layer is finally tied together by a suitable method, giving the non-woven material or the wadding its strength so that it can be handled and the material can be introduced into a machine for manufacturing absorbent articles, wound up on to a roll or the like.
Attempts have also been made to introduce fibers from fiber bales into an air flow and create a fiber layer on a vacuum wire, a so-called mat-former. The mat forming technique is a considerably easier and more robust technique than carding.
However, the mat-forming technique has proved to be too rough and insensitive and major problems have occurred when the fibers in the bale must be separated from one another without forming fiber flocks. Fiber flocks give rise to an uneven non-woven material or wadding material which does not function satisfactorily and is not aesthetically acceptable. The strength of the finished uneven material is also a problem.
There is therefore a need for a process and an arrangement, which from a continuous length of a thread bundle of fiber material can produce airborne fibers with an even distribution of fibers in the air flow without a significant incidence of fiber flocks in the air flow, so that the robust mat-forming technique can be used in the creation of a fiber layer.